Most bottles currently traded on the market contain one material in each bottle. It is, however, often necessary to mix two kinds of different materials together in a variety of industrial fields. For example, a coffee-based beverage may be mixed with sugar or cream powder therein; medicines and chemicals are similar cases.
In order to mix two different kinds of materials together, however, it is necessarily to buy two bottles containing the two different materials therein. In addition, a measuring instrument also needs to be bought for accurate measurement. Without such a measuring instrument, it is very difficult to keep the mixture ratio exact.